The present invention relates to a polishing apparatus capable of uniformly polish workpieces, e.g., wafers.
Many kinds of polishing apparatuses are known.
Generally, a polishing apparatus comprises: a polishing plate having an upper face, on which a polishing cloth is adhered; a holding head having a lower face, on which a workpiece is held so as to press the workpiece onto the polishing cloth; and a driving mechanism for relatively moving the polishing plate with respect to the holding head so as to polish a lower face of the workpiece.
A conventional polishing apparatus is disclosed in Japanese Patent No. 3158934. The polishing apparatus includes a holding head comprising: a main head section; a carrier provided in the main head section, the carrier holding a workpiece to be polished; a retainer ring provided outside of the carrier and coaxially arranged therewith, the retainer ring contacting the polishing cloth and holding an outer edge of the workpiece; a carrier pressure adjusting mechanism adjustably pressing the carrier toward a platen; and a ring pressure adjusting mechanism separated from the carrier pressure adjusting mechanism, the ring pressure adjusting mechanism adjustably pressing the retainer ring toward the platen.
In the polishing apparatus, the ring pressure adjusting mechanism is separated from the carrier pressure adjusting mechanism. Therefore, waving of the polishing close, which occurs near the workpiece, can be effectively prevented, so that overpolishing an outer edge of the workpiece can be effectively prevented.
These days, however, precise control of polishing pressure is required so as to further precisely polish the workpiece.